Cardiac rhythm management system providing control of pacing features with a reduced number of variables

ABSTRACT

A cardiac rhythm management system includes techniques for reducing the number of programmable variables associated with maximum pacing rate so that fewer variables are programmed and a reduction in possible parameter conflict is achieved. In an embodiment, a maximum pacing rate parameter replaces a plurality of conventional, separately programmable pacing parameters. For example, maximum tracking rate, maximum sensor rate, rate smoothing maximum pacing rate, atrial pacing preference maximum pacing rate, and ventricular rate regulation maximum pacing rate are replaced by a single maximum pacing rate with, if necessary, a sensor offset and an atrial pacing preference offset. In another example, rate smoothing maximum pacing rate, biventricular trigger maximum pacing rate and ventricular rate regulation maximum pacing rate are replaced by a single maximum pacing rate.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.09/739,091, filed on Dec. 15, 2000, now issued as U.S. Pat. No.6,618,618, the specification of which is incorporated herein byreference.

FIELD OF THE INVENTION

The present system relates generally to cardiac rhythm managementsystems and more particularly to a system reducing the number ofvariables associated with the maximum pacing rate.

BACKGROUND

Cardiac rhythm management systems provide therapy to a patient's heartto correct various forms of arrhythmias, such as tachyarrhythmias andbradyarrhythmias. One type of these systems includes an implantablecardiac rhythm management (“CRM”) device and a programmer forprogramming the CRM device. As the understanding of various types ofarrhythmias has grown since the inception of CRM devices over twodecades ago, so has the need to provide a greater variety of therapieswith the CRM device. This greater variety of therapies allows aphysician to closely tailor the therapy provided by the device to thespecific needs of the patient by programming various parameters of theCRM device. However, the number of programmable variables in CRM deviceshas grown along with the number and complexity of therapies.Accordingly, the physician must use the programmer to program numerousparameters of the CRM device to achieve the desired therapy. When it isdecided that a certain therapy should be altered, a correspondingprogrammable parameter is changed. The medical care provider must changethis programmable parameter and all related parameters. In someprogrammers, different parameters are displayed and accessible ondifferent screens of the programmer. Accordingly, the level ofcomplexity and knowledge of the CRM device and the programmer, which themedical care provider must understand when changing any programmableparameter so that all related parameters are appropriately changed, hasincreased with recent CRM devices. Consequently, there is a need in thefield of CRM systems to simplify the programming of the CRM device byreducing the number of programmable variables.

SUMMARY OF THE INVENTION

The present system provides, among other things, a cardiac rhythmmanagement system including techniques for reducing the number ofprogrammable parameters associated with a single variable. In oneembodiment, a plurality of maximum pacing rates are combined into asingle maximum pacing rate parameter. This maximum pacing rate parameteris used by different therapy processes. In another embodiment, thesystem includes setting a single maximum pacing rate with offsetstherefrom for select pacing features.

In another embodiment, the system includes a method of programming acardiac rhythm management device with a single maximum pacing rate for aplurality of therapies.

Other aspects of the invention will be apparent on reading the followingdetailed description of the invention and viewing the drawings that forma part thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating generally one embodiment ofportions of a cardiac rhythm management system and an environment inwhich it is used.

FIG. 2 is a schematic drawing illustrating one embodiment of a cardiacrhythm management device coupled by leads to a heart.

FIG. 3 is a schematic diagram illustrating generally one embodiment ofportions of a cardiac rhythm management device coupled to a heart.

FIG. 4 is a schematic diagram illustrating generally one embodiment of acontroller.

FIG. 5 is a schematic diagram illustrating an embodiment of the cardiacrhythm management device.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the spirit and scope of thepresent invention. The following detailed description is, therefore, notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims and their equivalents.

The present method and apparatus will be described in applicationsinvolving implantable medical devices including, but not limited to,implantable cardiac rhythm management systems such as pacemakers,cardioverter/defibrillators, pacer/defibrillators, and biventricular orother multi-site coordination devices. However, it is understood thatthe present methods and apparatus may be employed in unimplanteddevices, including, but not limited to, external pacemakers,cardioverter/defibrillators, pacer/defibrillators, biventricular orother multi-site coordination devices, monitors, programmers andrecorders.

FIG. 1 is a schematic drawing illustrating, by way of example, oneembodiment of portions of a cardiac rhythm management system 100 and anenvironment in which it is used. In FIG. 1, system 100 includes animplantable cardiac rhythm management device 105, which is coupled by anintravascular endocardial lead 110, or other lead, to a heart 115 ofpatient 120. Device 105 typically contains electronic circuitry. System100 also includes an external programmer 125 providing wirelesscommunication with device 105 using a telemetry device 130. Catheterlead 110 includes a proximal end 135, which is coupled to device 105,and a distal end 140, which is coupled to one or more portions of heart115.

FIG. 2 is a schematic drawing illustrating, by way of example, oneembodiment of device 105 coupled by leads 110A-B to heart 115, whichincludes a right atrium 200A, a left atrium 200B, a right ventricle205A, a left ventricle 205B, and a coronary sinus 220 extending fromright atrium 200A. In this embodiment, atrial lead 110A includeselectrodes (electrical contacts) disposed in, around, or near an atrium200 of heart 115, such as ring electrode 225 and tip electrode 230, forsensing signals and/or delivering pacing therapy (atrial pacing) to theatrium 200. Lead 110A optionally also includes additional electrodes,such as for delivering atrial and/or ventricularcardioversion/defibrillation and/or pacing therapy to heart 115.

In FIG. 2, ventricular lead 110B includes one or more electrodes, suchas tip electrode 235 and ring electrode 240, for delivering sensingsignals and/or delivering pacing therapy. Lead 110B optionally alsoincludes additional electrodes, such as for delivering atrial and/orventricular cardioversion/defibrillation and/or pacing therapy to heart115. Device 105 includes components that are enclosed in ahermetically-sealed housing, which is sometimes referred to as a can.Additional electrodes may be located on the can, or on an insulatingheader, or on other portions of device 105, for providing pacing and/ordefibrillation energy in conjunction with the electrodes disposed on oraround heart 115. Other forms of electrodes include meshes and patcheswhich may be applied to portions of heart 115 or which may be implantedin other areas of the body to help “steer” electrical currents producedby device 105. The present method and apparatus will work in a varietyof configurations and with a variety of electrical contacts or“electrodes.”

FIG. 3 is a schematic diagram illustrating generally, by way of example,one embodiment of portions of device 105, which is coupled to heart 115.Device 105 includes a power source 300, an atrial sensing circuit 305,an atrial therapy circuit 306, a ventricular sensing circuit 310, aventricular therapy circuit 320, and a controller 325.

Atrial sensing circuit 305 is coupled by atrial lead 110A to heart 115for receiving, sensing, and/or detecting electrical atrial heartsignals. Such atrial heart signals include atrial activations (alsoreferred to as atrial depolarizations or P-waves), which correspond toatrial contractions. Such atrial heart signals include normal atrialrhythms, and abnormal atrial rhythms including atrial tachyarrhythmias,such as atrial fibrillation, and other atrial activity. Atrial sensingcircuit 305 provides one or more signals to controller 325, via node/bus327, based on the received atrial heart signals. Such signals providedto controller 325 indicate, among other things, the presence of atrialfibrillation.

Atrial therapy circuit 306 provides atrial pacing therapy, asappropriate, to electrodes located at or near one of the atriums 200 ofheart 115 for obtaining resulting evoked atrial depolarizations. In oneembodiment, atrial therapy circuit 306 also providescardioversion/defibrillation therapy, as appropriate, to electrodeslocated at or near one, or both, of the atriums 205 of heart 115, forterminating atrial fibrillation and/or other atrial arrhythmias.

Ventricular sensing circuit 310 is coupled by ventricular leads 110B,110C to heart 115 for receiving, sensing, and/or detecting electricalventricular heart signals, such as ventricular activations (alsoreferred to as ventricular depolarizations or R-waves), which correspondto ventricular contractions. Ventricular lead 110C is similar to lead110B described above. Such ventricular heart signals include normalventricular rhythms, and abnormal ventricular rhythms, includingventricular tachyarrhythmias, such as ventricular fibrillation, andother ventricular activity, such as irregular ventricular contractionsresulting from conducted signals from atrial fibrillation. Ventricularsensing circuit 310 provides one or more signals to controller 325, vianode/bus 327, based on the received ventricular heart signals. Suchsignals provided to controller 325 indicate, among other things, thepresence of ventricular depolarizations, whether regular or irregular inrhythm.

Ventricular therapy circuit 320 provides ventricular pacing therapy, asappropriate, to electrodes located at or near one of the ventricles 205of heart 115 for obtaining resulting evoked ventricular depolarizations.In one embodiment, ventricular therapy circuit 320 also providescardioversion/defibrillation therapy, as appropriate, to electrodeslocated at or near one, or both, of the ventricles 205 of heart 115, forterminating ventricular fibrillation and/or other ventriculartachyarrhythmias.

Controller 325 controls the delivery of therapy by ventricular therapycircuit 320 and/or other circuits, based on heart activity signalsreceived from atrial sensing circuit 305 and ventricular sensing circuit310. Controller 325 includes various modules, which are implementedeither in hardware or as one or more sequences of steps carried out on amicroprocessor or other controller. Such modules are illustratedseparately for conceptual clarity; it is understood that the variousmodules of controller 325 need not be separately embodied, but may becombined and/or otherwise implemented, such as in software/firmware. Inan embodiment, the controller 325 includes a memory in which is storeddefault parameters, which are used by the programmer to control varioustherapies. One such default parameter may be a maximum pacing rate.

In general terms, sensing circuits 305 and 310 sense electrical signalsfrom heart tissue in contact with the catheter leads 110A-C to whichthese sensing circuits 305 and 310 are coupled. Sensing circuits 305 and310 and/or controller 325 process these sensed signals. Based on thesesensed signals, controller 325 issues control signals to therapycircuits, such as atrial therapy circuit 306 and/or ventricular therapycircuit 320, if necessary, for the delivery of electrical energy (e.g.,pacing and/or defibrillation pulses) to the appropriate electrodes ofleads 110A-C. Controller 325 may include a microprocessor or othercontroller for execution of software and/or firmware instructions. Thesoftware of controller 325 may be modified (e.g., by remote externalprogrammer 105) to provide different parameters, modes, and/or functionsfor the implantable device 105 or to adapt or improve performance ofdevice 105.

In one further embodiment, one or more sensors, such as sensor 330, mayserve as inputs to controller 325 for adjusting the rate at which pacingor other therapy is delivered to heart 115. One such sensor 330 includesan accelerometer that provides an input to controller 325 indicatingincreases and decreases in physical activity, for which controller 325increases and decreases pacing rate, respectively. Another such sensorincludes an impedance measurement, obtained from body electrodes, whichprovides an indication of increases and decreases in the patient'srespiration, for example, for which controller 325 increases anddecreases pacing rate, respectively. Any other sensor 330 providing anindicated pacing rate can be used.

FIG. 4 is a schematic diagram illustrating generally, by way of example,controller 325 that includes several different inputs to modify variousprogrammable parameters of the cardiac rhythm management device 105.However, only one of the inputs is a maximum pacing rate. Accordingly,in an embodiment controller 325 limits the maximum pacing rate for allof the therapies using the single maximum pacing rate input. Forexample, ventricle and atrium pacing are limited by the single maximumpacing rate. In another embodiment, rate smoothing, biventriculartriggered pacing and ventricular rate regulation are limited by thesingle maximum pacing rate. Ventricular rate regulation provides nearlycontinuous (i.e., to the desired degree) biventricular pacing when theventricular heart rate is substantially constant. In another embodiment,tracking rate, sensor rate, rate smoothing, atrial pacing preference,ventricular rate regulation are limited by the single maximum pacingrate. The maximum tracking rate limits how quickly the ventricle ispaced. The maximum sensor rate limits how fast a heart is paced based onsensed variables. The maximum rate smoothing prevents the pacing rateinterval from changing to quickly from one cycle to the next. It will beunderstood that the single maximum pacing rate is used to limit thepacing rate of more than one therapy, for example any two of thetherapies listed herein. Accordingly, a medical care provider need onlyinput the maximum pacing rate into the programmer 125 once. Programmer125 transmits the maximum pacing rate to the CRM device 105. Limited bythe single maximum pacing rate and based on other inputs, controller 325provides an output indication of pacing rate as a control signaldelivered to a therapy circuit, such as to atrial therapy circuit 306 orventricular therapy circuit 320. Atrial or ventricular therapy circuit306 or 320 issues pacing pulses based on one or more such controlsignals received from controller 325. Control of the pacing rate may beperformed by controller 325, either alone or in combination withperipheral circuits or modules, using software, hardware, firmware, orany combination of the like. The software embodiments provideflexibility in how inputs are processed and may also provide theopportunity to remotely upgrade the device software while stillimplanted in the patient without having to perform surgery to removeand/or replace the device 105.

In an embodiment of controller 325, the controller is configured toprovide biventricular triggered pacing, which is pacing one or bothventricles based on sensed ventricular contractions in one ventricle andtriggers ventricular pace in the other or both ventricles. Controller325 uses the maximum pacing rate to limit how fast it will pace one orboth of the ventricles to treat hemodynamic dysfunction, e.g. bundlebranch blocks or slow conduction in a portion of the ventricles, so asto improve the efficiency of the heart.

In another embodiment of controller 325, it is configured to receivemaximum pacing rate offsets from programmer 125. In some therapies it isnecessary to deviate from the single maximum pacing rate, for exampleatrial pacing preference such that an appropriate limit on how fast theatrium is paced by CRM device 105 or an appropriate limit as to when theatrium is paced by CRM device 105 are respectively imposed.

FIG. 5 shows an embodiment of CRM device 105 having hardware, e.g.circuitry, and software for a plurality of possible therapies 525. Eachof the possible therapies is adapted to pace a patient's heart. Eachtherapy is limited by a single maximum pacing rate 530. The maximumpacing rate 530 is a default maximum pacing rate stored in thecontroller or a downloaded maximum pacing rate, for example downloadedby programmer 125. Some therapies, e.g. atrial pacing preference,require a different maximum pacing rate than the other therapies.Offsets include a percentage offset from the maximum pacing rate, afractional offset, and a discrete number offset. The offsets canincrease or decrease the pacing rate from the maximum pacing rate.Additionally, the offsets can be different for different therapies.Offsets 536, 537 are loaded into the CRM device 105, for example byprogrammer 125. These offsets 536, 537 are used by CRM device 105 toincrease or decrease the maximum pacing rate for the therapies requiringa different maximum pacing rate. The CRM device 105 outputs a pacingsignal 540 that is limited by the maximum pacing rate 530 and, if any,offsets 536, 537.

In one embodiment of the system 100, programmer 125 stores which of thepossible therapies of a given CRM device 105 might require an offset.The programmer 125 prompts the user for an offset when these therapiesare activated in the CRM device 105. It is within the scope of thepresent invention for the offset to be an integer which is added orsubtracted from the single maximum pacing rate, or a fraction which ismultiplied times the single maximum pacing rate.

CONCLUSION

Previous CRM devices had separate maximum pacing rates for each therapy.CRM devices provide a plurality of therapies and hence a user mustprogram a corresponding plurality of maximum pacing rates. For example,such a CRM device would include a first input providing rate smoothingmaximum pacing rate, a second input providing biventricular triggermaximum pacing rate, and a third input providing a ventricular rateregulation maximum pacing rate. The inputs may further include maximumtracking rate, maximum sensor rate, rate smoothing maximum pacing rate,atrial pacing preference maximum pacing rate, ventricular rateregulation maximum pacing rates. A physician must accordingly programall of these various maximum pacing rates so that the CRM device willadminister the appropriate therapy which is limited by a specificmaximum pacing rate corresponding to the therapy. However, due to thenumerous different maximum pacing rates a physician may overlook one ofthe maximum pacing rate parameters when programming the CRM device,especially if the programmer accesses the different variables ondifferent display screens. This could result in the CRM deviceadministering unintended therapy to a patient by the CRM device relyingon an unintended maximum pacing rate that was not correctly set.

The above-described system provides, among other things, a cardiacrhythm management system including techniques for reducing the number ofvariables which must be adjusted to reduce potential conflictsparameters. In an embodiment, the parameters are maximum pacing rates.This embodiment attempts to reduce the occurrence of users failing toadjust all maximum pacing rates when it is necessary to do so.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. A cardiac rhythm management system, comprising: at least one module;and a communication unit configured to transmit to the at least onemodule a single maximum pacing rate signal associated by the at leastone module with a single maximum pacing rate for a plurality of pacingprocesses and an offset signal associated by the at least one modulewith an offset from the single maximum pacing rate for a pacing processof the plurality of pacing processes, wherein the transmitted maximumpacing rate limits at least two of the plurality of pacing processes andthe transmitted maximum pacing rate, as offset by the offset, limits thepacing process of the plurality of pacing processes.
 2. The system ofclaim 1, wherein said plurality of pacing processes includes at leastone of ventricular tracking, rate smoothing, tracking rate, sensor rate,ventricular rate regulation, and biventricular triggering, and whereinsaid plurality of pacing processes includes at least one of atrialsensing and atrial pacing preference.
 3. The system of claim 1, whereinsaid pacing process includes atrial pacing preference, wherein saidcommunication unit downloads the offset signal including an atrialpacing preference offset to offset said maximum pacing rate to determinea maximum atrial pacing preference rate.
 4. The system of claim 1,wherein the communication unit is adapted to wirelessly transmit theoffset.
 5. The system of claim 1, wherein the communication unit isadapted to prompt a user to input the offset.
 6. The system of claim 1,wherein the communication unit is adapted to transmit an atrial pacingpreference offset.
 7. The system of claim 6, wherein the atrial pacingpreference offset is a fraction of the single maximum pacing rate. 8.The system of claim 6, wherein the atrial pacing preference offset is apercentage of the single maximum pacing rate.
 9. The system of claim 6,wherein the atrial pacing preference offset is a discrete number offsetof the single maximum pacing rate.
 10. The system of claim 1, furthercomprising a memory adapted to store which of the plurality of pacingprocesses requires an offset from the single maximum pacing rate. 11.The system of claim 10, wherein the memory is adapted to store a defaultsingle maximum pacing rate.
 12. The system of claim 1, wherein thecommunication unit is adapted to receive the single maximum pacing rateas an input.
 13. The system of claim 1, wherein the communication unitincludes a telemetry device.
 14. A cardiac rhythm management system,comprising: at least one module; a communication unit configured totransmit to the at least one module a single maximum pacing rate signalassociated by the at least one module with a single maximum pacing ratefor a plurality of pacing processes and an offset signal associated bythe at least one module with an offset from the single maximum pacingrate for a pacing process of the plurality of pacing processes, whereinthe transmitted maximum pacing rate limits at least two of the pluralityof pacing processes and the transmitted maximum pacing rate, as offsetby the offset, limits the pacing process of the plurality of pacingprocesses; and a memory adapted to store which of the plurality ofpacing processes requires the offset from the single maximum pacingrate.
 15. The system of claim 14, wherein said plurality of pacingprocesses includes at least one of ventricular tracking, rate smoothing,tracking rate, sensor rate, ventricular rate regulation, andbiventricular triggering, and wherein said plurality of pacing processesincludes at least one of atrial sensing and atrial pacing preference.16. The system of claim 15, wherein said pacing process includes atrialpacing preference, wherein said communication unit downloads the offsetsignal including an atrial pacing preference offset to offset saidmaximum pacing rate to determine a maximum atrial pacing preferencerate.
 17. A cardiac rhythm management system, comprising: at least onemodule; a wireless communication unit configured to communicate to theat least one module a single maximum pacing rate signal associated bythe at least one module with a single maximum pacing rate for aplurality of pacing processes and an offset signal associated by the atleast one module with an offset from the single maximum pacing rate fora pacing process of the plurality of pacing processes, wherein thetransmitted maximum pacing rate limits at least two of the plurality ofpacing processes and the transmitted maximum pacing rate, as offset bythe offset, limits the pacing process of the plurality of pacingprocesses; and a memory adapted to store which of the plurality ofpacing processes requires the offset from the single maximum pacingrate.
 18. The system of claim 17, wherein said plurality of pacingprocesses includes at least one of ventricular tracking, rate smoothing,tracking rate, sensor rate, ventricular rate regulation, andbiventricular triggering, and at least one of atrial sensing and atrialpacing preference.
 19. The system of claim 17, wherein said pacingprocess includes atrial pacing preference, wherein said communicationunit downloads the offset signal including an atrial pacing preferenceoffset to offset said maximum pacing rate to determine a maximum atrialpacing preference rate.